Telephone system.



E. E. HINRICHSEN. TELEPHONE SYSTEM. APPLICATION FILED SEPT. 25. I911.

1 9g??? 0 Patented Sept. 3; 1918;

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EDWARD n. rrrnnionsnn, or New YORK, n. Y., rissrenon TO WESTERN ELECTRIC con- PANY, INCORPORATED, or new YORK, n. Y., A oonronarron or new YORK.

TELEPHONE SYSTEM.

Patented Sept. 3, 1918.

Application filed September 25, 1917. Serial No. 193,103.

To all whom it may concern:

Be it known that I, EDWARD E. HINRICI-I- SEN, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone systems and more particularly to such systems of the central energy type provided with apparatus for determining the idleor busy condition of the telephone lines of the telephone system.

The ob 'ect of this invention is to provide an improved busy testing means for such systems. In accordance with this invention, which is an improvement over that disclosed in a opending application of Clarence E. Fowler, Serial No. 193,102, filed September 25, 1917, there is provided a relay which when a busy test is being made is connected in 011'- cuit relation with the busy test relay to improve the operation of this busy test relay. When the usual listening key is actuated to connect the operators telephone set with an established connection between two subscribers, this relay is energized to disconnect the busy test relay from the circuit.

For a more complete understanding of this invention reference should be had to the following description considered in connection with the accompanying drawing illustrating one embodiment of this invention.

In the drawing there are shown two polystation telephone lines A and B, which terminate at a central office in a plurality of jacks, and a cord circuit C located at the central ofiice and employed for interconnecting the telephone lines. It is to be understood that many lines similar to lines A and B may terminate at the same central office and that a plurality of cord circuits may be provided for interconnecting such lines, but for convenience only the two lines and the one cord circuit are shown. It is believed that this invention will be thoroughly understood from a description of the operation of the system shown in the drawing and it will be so described.

One of the subscribers on line A in initiating the call removes the receiver from the switchhook, thereby causing the operation of line relay 5, which thereupon causes the lighting of line lamp 6. The operator upon observing the lighted condition of the line lamp 6 inserts answering plug 7 in one of the jacks associated with the line A, for eX- ample, jack 8. Cut-off relay 9 is thereupon operated to disconnect the line relay from the line and to efiace the line lamp 6. Answering supervisory relay 11 is also operated upon the connection of the answering plug 7 with thejaek S to remove the short circuit from resistance 12 and to establish a short-circuit about the answering supervisory lamp 13, thereby preventing the lighting of the lamp when the answering plug is inserted in the jack of the calling line.

The operator may now actuate listening key 15 to connect the operators telephone set 16 with the cord circuit. Assuming that the calling subscriber desires connection with another party on the same telephone line, the operator does not know that this second party is on the same line since there is provided for each station on the line a separate jack, and each station on the line is assigned a separate number. The operator, therefore, tests the line to determine whether it is idle or busy. In making this test, where the called party is on the same line with the calling party, the operator not only obtains the usual busy test, which is merely a single click in the operators receiver, but in addition there is produced in the receiver a tone which indicates that the called party is on the same line with the calling party. The manner in which this tone is produced in the operators receiver will now be described.

When the listening key 15 was actuated, contact 17 thereof was openedand contacts 18, 19, 20 and 21 closed. The closure of contacts 19 and 20 connected the operators telephone set to the cord circuit and the closure of contact 18 connected the busy test relay 25 (common to a plurality of cord circuits) with the tip conductor 26, which is the testing conductor for the calling end of the cord circuit. The closure of contacts 18 and 19 also connected both windings of relay 27 (common to a plurality of cord circuits) in the tip conductor 26 in series with winding 28 of repeating coil 29. In order to provide for the best transmission efficiency to voice currents, the windings of the repeating coil 29 must be of low resistance. Therefore, when the busy test relay is conplug 7 and jacks 8 nected with the tip conductor it is shunted by the low resistance winding of the repeating coil. It has, therefore, been extremely diilicult to obtain a busy test relay which would operate when the tip contact of the calling plug is engaged with the test termlnal of a jack. The resistance of the lefthand winding of relay 27 is low a nd of practically the same value as the winding of supervisory relay 31, while the righthand winding of relay 27 is of high resistance. When making a busy test both windings of relay 27 are connected in the tip conductor 26 in series with repeating coil winding 28 and very materially increases the resistance of the shunt about the busy test relay 25, so that when making a busy test relay 25 receives a greater amount of current, thereby insuring the proper operation of the relay. lVith the listening key actuated and the tip of the calling plug 32 brought into engagement with another jack33 of the calling line A, the busy test relay 25 is operated over a circuit from battery through the resistance 12, sleeve contacts of the answering plug 7 and the jacks 8 and 33, the tipcontact of the calling plug 32, tip conductor 26, contact 18 of listening key 15, lefthandcontact of relay 27, and the winding of busy test relay 25 to ground. While a circuit through relay 27 is established at the 211176 time, this relay does not receive suflicient current to cause it to attract its armatures. At the same time that relay 25 is operated a surge of current passes through both windings of relay 27 and through the receiver of the operators telephone set, thereby producing a click in this receiver. Busy test relay 25 in operating connects a source of tone supply 34 with the operators receiver 38 over a circuit from source 3 1 through a condenser 35, contact of busy test relay 25, contact 21 of listening key 15, con-- ductor 36, sleeve contacts of the answering and 33, tip contact of calling plug 32, tip conductor 26, contact 18 of listening key 15, windings of relay 27, induction coil winding 37, receiver 38, condenser 39, conductor 40, contact 20 of listening key 15, winding of supervisory relay 31, repeating coil winding 41, through battery to ground. A tone is thereby produced in the operators receiver 38, indicating to the operator that the called party is on the same line with the calling party. The relay 27 is not sui'ficiently energized when in the circuit just traced to attract its armatures. The connection with the called line and the signaling of the called station may be accomplished in any desired manner.

If the called party is one of the subscribers on line B, and line B is not busy, the engagement of the tip of the calling plug 32 with the test terminal of one of the jacks of line B does not produce a click in the op erators receiver? The operator thereupon restores the listening key to normal position, and inserts the calling plug 32 into one of the j a-cks oi the line B, whereupon the calling supervisory lamp a5 is lighted and cutoff relay ac operated. The called party may now be signaled in any desired manner. In responding, the called party removes the receiver from the switchhook, thereby causing the operation of the calling supervisory relay 31 which first removes a short circuit from resistance 47 and establishes a short circuit for calling supervisory lamp 45 which is thereupon eflaced.

If, while connection between lines A and B is established, and while thereceiver of the called party is removed from the switch.- hook, the operator actuates the listening key 15 to supervise the connection, the busy test relay 25 is thereupon automatically disconnected from the testing conductor in order not to produce any noise on the line. This is brought about in the following manner: Under the conditions mentioned, when listening key 15 is actuated, the windings of relay 27 are connected in series with'the tip conductor 26in the manner hereinbefore clescribed, and this relay now receives more current, whereupon it operates The circuit over Which this relay 27 operates may be traced from battery through repeating coil winding 11, winding of supervisory relay 31, ring contacts of calling plug 32 and jack 18, through the apparatus and switch hook contact of the called station, tip con tacts of jack 18 and calling plug 32, tip conductor 26, contact 18 of listening key 15, windings of relay 27, contact 19 of listening key 15, and repeating coil winding 28 to ground. Relay 27 in operating opens its left-hand contact, thereby preventing the connection of relay 25 with the tip conductor 26, and closes its right-hand contact, thereby to short-circuit its right-hand high resistance winding, which is thereupon removed from the talking circuit. The removal of this high resistance from the talking circuit is for the purpose of preventing the reduction in transmission efficiency. The left-hand winding of this relay, as before stated, is of practically the same resistance as the windingof supervisory relay 31, and

when connected in the tip conductor serves to balance the talking circuit. After supervising the connection the operator may restore the listening key 15 to normal position, whereupon the relay 27 is removed from the circuit.

At the conclusion of the conversation the subscribers may restore the receivers to the switchhook, whereupon supervisory relays 11 and 31 release to cause the lighting of the supervisory lamps 13 and 45, which serve as disconnect signals. The operator may then remove the plugs from the jacks whereupon all the apparatus is restored to normal condition. e

The windings of relay 27 serve as a resistance coil connected in parallel with the busy test relay 27 when making a busy test to insure the proper operation of the busy test relay. This relay 27 also serves as a disconnect relay for removing the busy test relay from the circuit when the operator is listening in on an established connection between two subscribers. By making it serve the double function, no additional apparatus is required in the circuit and the busy test relay due to the resulting improved operating conditions may be of simple rather than complex construction.

WVhat is claimed is:

1. In a telephone system, in combination, a poly-station telephone line terminating in a plurality of jacks, a cord circuit having its answering end connected with one of the jacks, a testing conductor for the calling end of the cord circuit, a repeating coil for the cord circuit having a winding connected in the testing conductor, an opera tors telephone set, a listening key for connecting the operators telephone set with the cord circuit, a relay. connected in series with the repeating coil winding by actuation of the key, a source of tone-supply, and a busy test relay connected wlth the testing conductor and in parallel'vvith the first relay and the repeating coil winding upon the actuation of the key and responsive to the engagement of the testing conductor with the test terminal of another jack to connect the source of tone supply in circuit with the receiver of the operators set.

2. In a telephone system, in combination, a plurality of poly-station telephone lines, each terminating in a plurality of jacks, a plurality of cord circuits, one of the cord circuits having its answering end connected with a jack of one of the telephone lines, a testing conductor for the calling end of each cord circuit, an operators telephone set, a listening key for the engaged cord circuit for connecting the operators telephone set therewith, a relay common to the cord circuits connected in series with the testing conductor by the actuation of the key, a source of tone supply, and a'busy test relay connected with the testing conductor in parallel with the first-mentioned relay upon actuation of the key and responsive to the engagement of the testing conductor with the test terminal of another jack of the engaged line to connect the source of tone supply in circuit with the receiver of the op erators telephone set. V

3. In a telephone system, in combination, a plurality of telephone lines each terminating in a plurality of jacks, a cord circuit having its answering end connected with a jack of one of the lines, a combined testing and talking conductor for the calling end of the cord circuit, an operators telephone set, a listening key for connecting the operators telephone setwi-th the cord circuit, a source of tone supply, a busy test relay connected with the testing conductor by the actuation of the key and responsive to the engagement of the testing conductor with another jack of the engaged lme for connecting the source of tone supply incircuit with the receiver of the operators telephone set, and a relay a plurality of telephone lines each terminating in a plurality of jacks, a cord circuit, a combined testing and talking conductor for the calling end of the cord circuit, a busy 1 test relay adapted to be connected with the testing conductor for determining the idle or busy condition of a line, an operators telephone set, a listening key for connecting the operators telephone set with the cord circuit, and a relay connected in series with the talking and testing conductor by the actuation of the key and energized whenthe calling. end of the cord circuitis connected with a telephone line to disconnect the busy 7 test relay from the testing conductor;

5. In a telephone system, in combination,

7 a plurality of telephone lines each terminating in a plurality of jacks, a cord circuit having its answering end connected with a jack of one of the lines, a combined talking and testing conductor for the calling end of the cord circuit, an operators telephone set, a listening key for connecting the operators telephone set with the cord circuit, a source of tone supply, a busy test relay connected with the testing conductor by the actuation of the key and responsive to the engagement of the testing conductor with another jack of the engaged line for connecting the source of tone supply in circuit with the receiver of the operators telephone set, and a disconnect relay having aTplurality of windings connected in series with the combined talking and testing conductor-and in parallel with the busy test relay by the actuation of the key, said disconnect relay being unresponsive to the engagement of the testing conductor with the testtermina] of a jack, but responsive when the calling end of the cord circuit is inserted into a jack of one of the telephone lines to disconnect the busy test relay from the testing conductor and to remove one of its windings from the circuit.

6. In a telephone system, in combination, a plurahty of telephone lines each terminat- 5 the cord circuit, an operators telephone set,

ing in a plurality of jacks, a cord circuit having its answering end connected with the jack of one of the lines, a combined talking and testing conductor for the calling end of combined talking and testing conductor by the actuation of the key and energized when the cord circuit is connected with the jack of another line to disconnect the busy test relay from the testing conductor.

In Witness whereof, I hereunto subscribe my name this 19th day of September A. 1)., 1917.

a listening key for connecting the operators telephone set With the cord circuit, a busy test relay connected with the testing conductor by the actuation of the key, and a 10 disconnect relay connected in series With the EDWARD E. HINRICHSEN.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

' Washington, D. O." 

